1. Field of the Invention
The present invention relates to communication systems and methods, and in particular to switching systems and methods.
2. Description of the Related Art
Internet demand has pushed bandwidth growth at a long distance carrier's Point Of Presence (POP)(e.g., generally in the form of a switch or router) by five times a year. At this rate, the bandwidth requirement at a POP will be several terabits/sec. The bandwidth explosion is not limited to the Internet backbone. One-gigabit Ethernets have been proposed, and 10 gigabits per second (Gbps) links may be needed to connect the Ethernets.
On the transmission side, Dense Wavelength Division Multiplexing (DWDM) technology has been developed in an attempt to meet the tremendous bandwidth demand. With DWDM technology, a hundred wavelengths may be put on a single fiber, and there is potentially an almost infinite capacity for transmission. In contrast, the capacity of switches and routers has not grown at the same rate, and is significantly lagging behind. The challenge posed by DWDM technology for switching is not just capacity. DWDM also created an explosion in the number of ports for a switch to handle. A hundred wavelengths mean a hundred ports will terminate on a switch. If a switch or router has ten terminating fibers, the switch or router needs to handle 1000 ports.
To keep up with transmission, it is desirable for a switching system to accommodate hundreds or even thousands of ports. The switching system should possess a simplicity that matches the system's ability to scale. Otherwise, a thousand-port switching system may collapse on its own complexity.
Some existing switching systems are designed with single-stage crossbars, which attempt to handle about 32 ports. Some existing switching systems include N. McKwown, “A Fast Switched Backplane For A Gigabit Switched Router,” Business Communications Review, December 1997, “Cisco 75000 Router Series datasheet” from Cisco, and “Enhanced TT1 Switch Fabric Datasheet” from PMC-Sierra Inc. But these systems cannot scale, i.e., the structure and scheduling algorithm(s) of these systems prevent the systems from handling more than 32 ports.